One of the problems presented in building a staircase is to provide for precise placement of horizontal steps and vertical risers on supporting stringers. This requires making horizontal and vertical cuts in diagonally extending stringers at required locations. Placement of lines on the stringers for making cuts at these locations require determination of vertical rise and horizontal run distances for the particular staircase and inscribing the lines on the stringers with the aid of a suitable square or similar tool placed in a position responsive to rise and run distances.
Conventional framing squares have been used for laying out stringers for stairs. In using such a square, however, the carpenter must hold the framing square on a piece of lumber while lining up the proper numbers on each of the blades with the edge of the board. This operation must be repeated for each step and can be tedious and time consuming as well as highly susceptible to mistakes due to misreading and marking the wrong setting. Thus, a need exists for a specialized square which can be used without making separate readings for each step.
Various types of special templates and squares for laying out stair stringers are disclosed in prior patents. U.S. Pat. No. 4,882,846, issued Nov. 28, 1989, to Reed discloses a stair building template using a plurality of rectangular-shaped horizontal and vertical members held in right-angle relationship. Swanson in U.S. Pat. No. 4,513,510, issued Apr. 30, 1985, discloses a tool having a triangular-shaped flat member with a tee along one edge and a layout bar alignable with slots in a side member. In use this tool is held against the edge of a stringer, and contact is made by stops which make contact over only a small area. A stairs layout tool in which a T-square is mounted on the leg of a conventional framing square is disclosed in U.S. Pat. No. 3,478,434, issued Nov. 18, 1969, to Catalano. Wright in U.S. Pat. No. 4,280,282, issued Jul. 28, 1981, discloses a triangular template with a movable outside portion of one of the legs. Adjustments in the position of the outside portion are made by engaging a selected one of a series of connections and by movement of a pivoting fulcrum. These tools present disadvantages in their complexity and difficulty of use in certain respects. For example, two of the patents require holding the tool, once settings have been made, against a side edge surface of a stringer during scribing, with contact of the tool and stringer being made over only a small area. This results in the tendency of the tool to slip and produce erroneous readings. A tool providing greater contact over an elongated, flush area is needed to avoid this problem. Other desired features include simplicity, ease of use, effectiveness, and a compact size such that a carpenter would be willing to carry the tool around in a toolbox so as to be available when needed.